Recently, the market of portable information apparatuses such as a portable telephone and an electronic mail terminal has been rapidly expanding. With progress in the miniaturization and in the weight reduction of these portable information apparatuses, the power source of the apparatus is also required to be miniaturized and to be made lighter in weight. A lithium ion secondary battery having a high energy density is used for these portable information apparatuses. Further, there is a need for a battery capable of providing higher capacity.
As for an air battery using oxygen in the air as a positive electrode active material, it is not necessary to integrate the positive electrode active material in the battery. Thus, a higher capacity can be expected. A lithium/oxygen organic electrolyte battery is described in Non Patent Literature 1. The lithium/oxygen organic electrolyte battery comprises a positive electrode containing MnO2 and carbon black, a negative electrode formed of lithium, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte which is immersed in the positive electrode, the negative electrode and the separator.
Patent Literature 1 suggests that a hydrophobic ionic liquid is used as a nonaqueous electrolyte of a nonaqueous electrolyte air battery. Patent Literature 2 suggests that a solid electrolyte is applied to the nonaqueous electrolyte of the nonaqueous electrolyte air battery.
On the other hand, Non Patent Literature 2 points out a problem that, according to a lithium air battery using an organic electrolyte, the accumulation of Li2O (a solid reaction product) at the positive electrode results in blocking of the pores of the positive electrode, and thus the discharge reaction is terminated. In order to avoid this problem, in the air battery of Non Patent Literature 2, it is suggested that the solid electrolyte is arranged as the separator between the positive electrode and the negative electrode, and the organic electrolyte is used for the negative electrode, and a water-based electrolyte is used for the positive electrode.